Intumescent fire-retarding composition comprising ammonium derivatives of glyoxylic acid

ABSTRACT

Water-soluble mono- and diammonium derivatives of glyoxylic acid are prepared and used as intumescent fire-retarding and heatinsulating materials.

United States Patent Masciantonio et a1.

[ 1 June 6, 1972 INTUMESCENT FIRE-RETARDING COMPOSITION COMPRISING AMMONIUM DERIVATIVES OF GLYOXYLIC ACID Inventors: Philip X. Masciantonio, Penn Township,

Appl. No.: 62,721

US. Cl ..252/8.1, 106/15 FP, 117/136, 1 17/137 Int. Cl. ..C09d 5/18, C09k 3/28 [58] FieldofSearch ..252/8.1; 106/15 FP; 117/136, 117/137; 260/526 R, 534 M, 2.5 PF

[56] References Cited UNITED STATES PATENTS 2,347,031 4/1944 Cupery "117/137 Primary Examiner-John T. Goolkasian Assistant Examiner-D. J. Fritsch Attorney-Gene Harsh [5 7] ABSTRACT Water-soluble monoand diamrnonium derivatives of glyoxylic acid are prepared and used as intumescent fire-retarding and heat-insulating materials.

7 Claims, No Drawings INTUMESCENT FIRE-RETARDING COMPOSITION characteristic of these compounds which makes them excel- COMPRISING AMMONIUM DERIVATIVES OF lent fire-retarding and heat-insulating agents is their ability to GLYOXYLIC ACID produce a voluminous polymeric tliuuc-rcturding thcrnmset foam which does not itself flame and most importantly, BACKGROUND OFTHE INVENTION 5 evolves a flame-extinguishing gaseous product, but which The monoand diammonium derivatives of glyoxylic acid gives off Very little Smoke of noxious fumesare not new to chemical literature, although the structure of DETAILED DESCRIPTION these compounds appears not to have been definitely resolved. Debus, who discovered glyoxylic acid in 1856 (Phil. Mag, 12, 361 [1856] speculated that the product of reac- Studies were conducted to determine the structure of the ammonia derivatives of glyoxylic acid. As stated above, two

tion of equimolar amounts of ammonia and glyoxylic acid was Structures the ammonium salt: have been proposed; ammonium glyoxylatc O O yO O\ //O c c% Nmon h II ONH4 H O H H ONH4 and hydroxyglycinc (hydroxyamino acetic acid). glyoxylic acid ammoniurnhydroxide OH O ammonium glyoxylate H2NCC Later experimenters (W. H. Perkin in Debus, J. Chem. Soc. l 0 85, 1386 1904 speculated that this was incorrect and that H H the correct reaction The results of our studies support the isomeric structure, hydroxygl cine, for the com ound repared from one mole of O O OH O y p p x y g} ammonia. NH4OH H2N The hydroxyglycinc compound can react with a H OH H OH second mole of ammonia to give the ammonium salt glyoxylic acid -I- ammonium hydroxide HO O h d o. l y l' xyg ycine It appears that little interest has existed in this compound \ONHr since its discovery by Debus, and his assignment of structure has persisted throughout subsequent literature. In 1934, for example, Desnuelle and Fromageot (Bull. Soc. Chem., 59, 700 [1934] reported the preparation of glycine by catalytic hydrogenation of ammonium glyoxylate.

Various organic and inorganic compounds, both alone and in combination with each other, have been tested as intumescent agents. Ammonium phosphate, vermiculate, casein, starch, benzene sulfonylhydrazide, polyamide resins, paraformaldehyde, and glycine have all been shown to produce some degree of intumescence, but only a few are of real value. A

Both of these compounds are thermally unstable, resulting in the elimination of gaseous products and producing a volu- 3 5 minous, thermally stable thermosetting polymer foam.

The compounds of the present invention are prepared by reacting glyoxylic acid with one or two molecular equivalents of ammonia in an aqueous system. The preferred amount of ammonia is that stoichiometric with the glyoxylic acid. The

40 amount of water solvent can range from 20 to 100 weight percent of the glyoxylic acid, the preferred amount being from to 100 weight percent. The reaction is conducted, with coolcombination of glycine, starch, and ammonium phosphate, for at from to C, the Preferred range being from to example, has given good results, but the use f glycine is 10 C. After addition of one molecular equivalent of ammonia li i d b i hi h cost, I other cases, excessive smoke 4 is completed, the monoammonium derivative is recovered by production is a problem, as is the production of toxic gaseous filtration, or a second equivalent of ammonia is added to make pyrolysis products. the diammonium derivative. The diammonium is recovered as Accordingly, it is an object of this invention to provide lowa glassy solid by flash evaporation of the water solvent. A cost intumescent agents, which, on exposure to flame or heat, crystalline product is obtained by removing 85 to 95 percent evolve flame-extinguishing gaseous products, and which con- 50 of the water by flash evaporation at 45 C and 10 mm Hg. and comitantly polymerize to produce an infusible, thermally Staallowing the syrup to stand for 18 to 24 hours at ambient tern ble polymer foam that acts as a barrier to dissipate heat and to perature. prevent flame spread. In accordance with the invention, the compounds can be used as the intumescent component alone or in combination with other intumescent agents in formulating fire-retardant It is a further object to provide intumescent agents that are comparatively non-smoking and which do not, during pyrolysis, yield significant amount of particular y toxic 38560115 paints. Other components of such formulations could include products such as hydrogen cyanide, cyanogen, an h like, inert fillers, colorants, thixotroping agents, agents that and which therefore are seful as mP M alone in promote water resistance, and agents that prevent mildewing.

combination with other in me n 1' other agents in Examples of other intumescent agents suitable for use with firepr0Ofingf l'i11 n the compounds of our invention are ammonium phosphate,

It is also an object of this invention to provide coating coml i d Starch positions suitable for coating on substrates to provide fire-re- Especially i bl fill are l ili i h lli g and heatinsulating Propertiea barytes, asbestos, and various metal oxides excepting those of 5 the alkaline earth metals.

SUMMARY OF THE INVENTION Especially suitable colorants are iron oxides, lead chromate Novel intumescent fire-retarding and heat-insulating agents and chromium oxide.

comprising the monoand diammonium derivatives of glyox- Polyvinyl alcohols, carboxy methyl cellulose, and pyrogenic ylic acid are presented. These compounds are useful in the silicas are thixotropic agents which can be advantageously fireproofing of structural members, especially in high rise used in conjunction with the compounds of our invention. structures. They may be used alone or they may be combined A preferred water resistance agent is dimethyl diethoxwith other intumescent agents, fillers, colorants, thixotroping ysilane. Preferred anti-mildew agents are copper 8-quinolinate agents, anti-mildew agents, and agents to improve water reand bis(tri-n-butyltin) oxide.

sistance. Application may be by simple coating of the member In these compositions the monoor diammonium derivative to be fireproofed as by spraying, brushing, dipping, etc. The of glyoxylic acid can comprise from to about 35 weight percent of the composition, with from about 60 to about 45 weight percent of the composition being preferred.

It is not possible to state with particularity the amounts of the other materials which may be present in the composition as this is dependent upon the intended application. Thus, when used in a dry location, mildew and water resisting agents would not be necessary. Colorants may be used in exposed locations but would not be necessary where the coated member will be hidden. In Examples 3 and 4, we have formulated representative compositions using the diammonium derivative of glyoxylic acid alone and in conjunction with other agents, from which it is obvious that the formulation may vary widely, provided always that a minimum of 35 weight percent of the composition is the monoor diammonium derivative of glyoxylic acid.

While both subject compounds are operable as intumescent agents, the diammonium derivative produces a more voluminous foam because of its greater NH content, and is preferred.

The following examples illustrate our invention, but are not intended to be limiting.

EXAMPLE 1 To prepare the monoammonium derivative, glyoxylic acid monohydrate (92 g, 1.0 mole) in water (92 ml) is cooled by a salted ice bath to between and C. A solution (28 percent) of ammonium hydroxide (67.5 ml, 1 mole Nl-l is added at a rate sufficient to maintain a temperature of about 5 C. Since the reaction is very exothermic, this requires an addition period of about 1 hour. When addition is complete, acetone (400 ml) is added. The white crystalline product is collected by filtration and dried over calcium chloride under reduced pressure. Melting point of the product is 100 C with decomposition. Product weight is 80 g.

EXAMPLE 2 To prepare the diammonium derivative of glyoxylic acid, the procedure of Example 1 is followed, but twice the amount of ammonium hydroxide is added. The reaction temperature is allowed to rise to 40 C on addition of the second mole of ammonium hydroxide. The reaction solution is flash-evaporated at 45 C and mm Hg until about 90 percent of the water solvent is removed. A thick, syrupy product is obtained, which gradually crystallizes during 24 hours at ambient temperature.

EXAMPLE 3 To demonstrate the intumescent and flame-retarding properties of the subject compounds, a fir-inch dowel rod is coated with l/ 16-inch coating (dry thickness) of the syrupy product of Example 2 and allowed to dry at ambient temperature. Samples of the coated rod and uncoated rod are exposed to the oxidizing flame from a Meeker burner at such a distance that kindling of the uncoated rod occurs in 2 seconds, with burn-through in 1 minute. The coated sample develops a voluminous polymeric foam. There is no kindling after as long as 10 minutes of exposure to the flame.

EXAMPLE 4 The procedure of Example 3 is followed using the following coating formulations prepared by mixing with high speed stirring, the following ingredients with sufficient water to give a syrupy consistency:

Mica (325 mesh) Bentonite Copper hydroxyquinolinate The coating was l/32-inch thick. Both formulations develop a voluminous foam and do not kindle.

EXAMPLE 5 To prepare a simple intumescent paint, the crystallized product (48 g) of Example 2 is pulverized with bentonite clay (16.0 g) and Bentone-l l, a quartenary amine derivative of bentonite clay (2.0 g). The mixture is triturated with water (18 ml) and finally milled in a colloid mill to obtain a highly dispersed homogeneous mixture. The insulative ability of the paint is tested by coating steel cylinders with the above formulation, drying, and exposing the cylinders to a temperature of 1,600 F in an electric furnace. The cylinders are center-bored to accommodate a thermocouple, and the rate of heat transfer to the cylinders is then calculated from temperature data obtained. The results are as follows:

Rate of Heat Transfer As is apparent from the foregoing specification, the method of the present invention is susceptible of being embodied in various attractions and modifications which may differ particularly from those that have been described in the preceding specification and description. For this reason, it is to be un derstood that the foregoing is intended to be illustrative and is not to be construed as limiting the present invention except as set forth and defined in the appended claims.

We claim:

1. A method of coating articles to render them flame-retarding and heat-resistant comprising applying a coating to said article comprising an intumescent agent selected from the group consisting of the monoammonium and diammonium derivatives of glyoxylic acid and mixtures thereof.

2. The method of claim 1 wherein the intumescent coating is at least l/32-inch thick.

3. An improved intumescent fire-retarding and heat-insulating composition comprising an intumescent agent selected from the group consisting of the monoand diammonium derivatives of glyoxylic acid and mixtures thereof, a filler, and a thixotropic agent.

4. The composition of claim 3 wherein the intumescent agent is the diammonium derivative of glyoxylic acid, the inert filler is asbestos, the thixotropic agent is a mixture of pyrogenic silica and an acrylic emulsion.

5. The composition of claim 3 wherein the thixotropic agent is selected from the group consisting of polyvinyl alcohols, carboxymethyl cellulose, pyrogenic silica and mixtures thereof.

6. The composition of claim 3 wherein the filler is selected from the group consisting of talc, silica, mica, pyrophyllite, barytes, asbestos, and metal oxides excepting the oxides of alkaline earth metals and mixtures thereof.

7. The composition of claim 6 wherein a colorant selected from iron oxide, lead chromate and chromium oxide is added. 

2. The method of claim 1 wherein the intumescent coating is at least 1/32-inch thick.
 3. An improved intumescent fire-retarding and heat-insulating composition comprising an intumescent agent selected from the group consisting of the mono- and diammonium derivatives of glyoxylic acid and mixtures thereof, a filler, and a thixotropic agent.
 4. The composition of claim 3 wherein the intumescent agent is the diammonium derivative of glyoxylic acid, the inert filler is asbestos, the thixotropic agent is a mixture of pyrogenic silica and an acrylic emulsion.
 5. The composition of claim 3 wherein the thixotropic agent is selected from the group consisting of polyvinyl alcohols, carboxymethyl cellulose, pyrogenic silica and mixtures thereof.
 6. The composition of claim 3 wherein the filler is selected from the group consisting of talc, silica, mica, pyrophyllite, barytes, asbestos, and metal oxides excepting the oxides of alkaline earth metals and mixtures thereof.
 7. The composition of claim 6 wherein a colorant selected from iron oxide, lead chromate and chromium oxide is added. 